Ultrahigh-resolution fiber-optic image guides derived from microstructured polymer optical fiber preforms

Ultrahigh-resolution fiber-optic image guides-fused image fiber, faceplate, and taper-were fabricated by using microstructured polymer optical fiber (MPOF) preforms composed of two polymers: polymethylmethacrylate and polystyrene. The pixel diameter in the resultant MPOF-based image guides was as small as 3 mu m. The imaging capabilities of these types of fiber-optic elements were demonstrated. (C) 2009 Optical Society of America

Ultra-dry oxygen atmosphere to protect tellurite glass fiber from surface crystallization

In this study we report on surface crystallization phenomena and propose a solution for the fabrication of long and robust tellurite glass fibers. The bulk tellurite glasses of interest were prepared by melting and quenching techniques. Tellurite glass preforms and fibers were fabricated by suction casting and rod-in-tube drawing methods, respectively. The surfaces of the tellurite bulk glass samples and of the drawn fibers prepared under different controlled atmospheres were examined by X-ray diffraction. When the tellurite glass fibers were drawn in ambient air containing water vapor, four primary kinds of small crystals were found to appear on the fiber surface, alpha-TeO(2), gamma-TeO(2), Zn(2)Te(3)O(8) and Na(2)Zn(3)(CO(3))(4)center dot 3H(2)O. A mechanism for this surface crystallization is proposed and a solution described, using an ultra-dry oxygen gas atmosphere to effectively prevent surface crystallization during fiber drawing. (C) 2010 Elsevier B.V. All rights reserved.

剪切对iPP结晶行为的影响

在聚合物的生产加工过程中，样品会不可避免地受到剪切流动作用，剪切流动诱导聚合物结晶一直是高分子的基础领域之一。受到剪切作用后，聚合物分子链取向生成与静态结晶时不同结构形态的晶体。聚丙烯具有质量轻，耐热性、耐腐蚀性好及易进行各种成型加工等优点，是应用最广泛的工业化生产的聚合物之一。因此研究聚丙烯在外力场中的性质是目前的热点之一。本论文通过剪切仪，偏光显微镜，X一射线衍射仪，DSC等各种实验仪器和实验手段研究了剪切对添加不同含量β成核剂的聚丙烯的晶体形态和晶体结构的影响；剪切对等规聚丙烯晶体形态、结晶动力学的影响以及振荡剪切对等规聚丙烯晶体形态和晶体结构的影响。通过对实验结果的分析研究，我们发现在134 ℃结晶时，对不同β成核剂含量的样品，成核剂含量越高，晶体尺寸越小，密度越大；并且样品的结晶温度越高。对样品施加剪切后我们发现虽然不同含量成核剂的样品中β晶的生成机制不同，但剪切都会抑制β晶的生成。同样的，在其他结晶温度，剪切也会抑制β的生成。通过不同的剪切方法，我们发现松弛是影响剪切诱导聚丙烯结晶行为的重要因素。采用适当的剪一切方法可以改变iPP晶体形态，生成纤维晶，增加晶体密度；并且可以力Fl速球晶生长速率。对实验结果进行拟合发现修正的Lauxizen-Hoffinan理论可以很好的用于描述剪切之后iPP的球晶生长结晶动力学。我们认为剪切加速结晶速度的原因是剪切增加了iPP熔体的自由能，利用DE-IAA模型计算得到的△G_f与实验结果基本一致。同时我们发现通过Arrhennius公式推导得到的iPP结晶温度范围内的零剪切粘度刃。适用于修正后的Laulizen-Hoffnan结晶动力学理论。我们通过分别变化应变和频率测定了振荡对iPP结晶行为的影响，结果发现在一定的频率下，应变对iPP形态影响很大，当应变达到200％时，生成纤维晶。并且随着应变的增加，iPP的晶体密度增加，而且分子取向明显增加。固定应变（100%），改变频率，我们发现在低频率时随着频率的增加，球晶密度增加，而后频率继续增加，球晶密度变化不大；并且频率的变化对iPP晶体形态没有影响，只生成球晶。另外振荡剪切同样能够诱导聚丙烯生成β晶，在一定的频率下，随着应变的增加，β晶结晶度增加；但是固定应变，增加振荡频率，我们发现p晶结晶度几乎不随着频率的变化而变化。

Thermally Stable Guest-Host Polyetherketone Poled Polymer for Electro-Optical Applications

The high glass transition temperature polymer polyetherketone doped with disperse red 13 (DR13/PEK-c) has been prepared by the spin-coating method. Through in situ second-harmonic generation, the corona poling temperature was optimized by measuring the temperature dependence of the in situ second-harmonic generation signal intensity under the poling electric field. The linear electro-optic coefficients of the poled polymer films have been determined at 632.8 nm by using a simple interferometric technique. The polymer system was measured after 13 000 h, and found that it remained at 80% of its initial value.

An investigation on fiber coupled polymer waveguide for electro-optic modulator

A novel crosslinkable polyurethane is used as the core layer of the electro-optic(E-O) modulator. The refractive index and dispersion of this material have been detected by analyzing the F-P oscillation in transmission spectra. Calculated results from the effective index method are given to design the Mach-Zehnder and straight 5-layer ridge wave-guide device (including the metal electrodes). With light at 1.31 mum being fiber coupled into waveguide, the mode properties of these devices have been demonstrated in a micron control system. The guided mode is accordant with the theoretical analysis.

Aluminum induced crystallization of strongly (111) oriented polycrystalline silicon thin film and nucleation analysis

A polycrystalline silicon thin film was fabricated on glass substrate by means of aluminum induced crystallization (AIC). Al and alpha-Si layers were deposited by magnetron sputtering respectively and annealed at 480A degrees C for 1 h to realize layer exchange. The polycrystalline silicon thin film was continuous and strongly (111) oriented. By analyzing the structure variation of the oxidation membrane and lattice mismatch between gamma-Al2O3 and Si, it was concluded that aluminum promoted the formation of (111) oriented silicon nucleus by controlling the orientation of gamma-Al2O3, which was formed at the early stage of annealing.

Fluorescence Hydrogen Peroxide Probe Based on a Microstructured Polymer Optical Fiber Modified with a Titanium Dioxide Film

A highly sensitive microstructured polymer optical fiber (MPOF) probe for hydrogen peroxide was made by forming a rhodamine 6G-doped titanium dioxide film on the side walls of array holes in an MPOF. It was found that hydrogen peroxide only has a response to the MPOF probe in a certain concentration of potassium iodide in sulfuric acid solution. The calibration graph of fluorescence intensity versus hydrogen peroxide concentration is linear in the range of 1.6 x 10(-7) mol/L to 9.6 x 10(-5) mol/L. The method, with high sensitivity and a wide linear range, has been applied to the determination of trace amounts of hydrogen peroxide in a few real samples, such as rain water and contact lens disinfectant, with satisfactory results.

Cellulose acetate polymer film modified microstructured polymer optical fiber towards a nitrite optical probe

A novel microstructured polymer optical fiber (MPOF) probe for nitrites (NO(2)(-)) detection was made by forming rhodamine 6G (Rh 6G)-doped cellulose acetate (CA) on the side wall of array holes in a MPOF It was found that the MPOF probe only have a response to nitrites in a certain concentration of sulfuric acid solution The calibration graph of fluorescence intensity versus nitrites concentration was linear in the range of 2.0 x 10(-4) g/ml-5.0 x 10(-3) g/ml. The method possesses case of chemical modification, low cost design, and potential for direct integration with existing instrumentation, and has been applied to the determination of nitrites in real samples with satisfactory results. (C) 2010 Elsevier B.V. All rights reserved

Brownian dynamics simulation of the crystallization dynamics of charged colloidal particles

Crystal formation process of charged colloidal particles is investigated using Brownian dynamics (BD) simulations. The particles are assumed to interact with the pair-additive repulsive Yukawa potential. The time evolution of crystallization process and the crystal structure during the simulation are characterized by means of the radial distribution functions (RDF) and mean square displacement (MSD). The simulations show that when the interaction is featured with long-range, particles can spontaneously assemble into body-centered-cubic (BCC) arrays at relatively low particle number density. When the interaction is short-ranged, with increasing the number density particles become trapped into a stagnant disordered configuration before the crystallization could be actualized. The simulations further show that as long as the trapped configurations are bypassed, the face-centered-cubic (FCC) structures can be achieved and are actually more stable than BCC structures. (C) 2010 Elsevier Inc. All rights reserved.